136 Thomas Henry Huxley 



the less, there are huudreds of thousands of species of 

 Ijirds between these two types. It is not surprising 

 that to reduce this vast assemblage of similar creatures 

 to an ordered system of classification has proved one of 

 the most difficult tasks attempted by zoologists. Before 

 Huxley, it had been attempted by a number of distin- 

 guished zoologists ; but, for the most part, these had 

 relied too much on merely external characters and on 

 superficial modifications in obvious relation to habits. 

 When Huxley, in the course of a set of lectures on 

 Comparative Anatomy, was about to approach the sub- 

 ject of birds he was asked by a zoologist how he pro- 

 posed to treat them. " I intend," he repHed, " to 

 treat them as extinct animals." By that he meant 

 that it was his purpose to make a prolonged study of 

 their skeletal structures the basis of his grouping, fol- 

 lowing the lines which Cuvier, Owen, and he himself 

 had pursued so successfully in the case of the fossil 

 remains of vertebrates. The result was that this first 

 systematic study of even one set of the anatomical 

 characters of the group completely reformed the method 

 by which all subsequent workers have tried to grapple 

 with the problem ; ornithology was raised from a pro- 

 cess akin to stamp-collecting to a reasoned scientific 

 study. The immediate practical results were equally 

 important. He was able to shew that among the in- 

 numerable known forms there were three grades of 

 structure. The lowest had already been recognised and 

 named by Haeckel ; it consisted of the Saururse, or rep- 

 tile-like birds, and contained a single fossil form, Ar- 

 chaeopteryx, distinguished front all living birds by the 

 presence of a hand-like wing in which the metacarpal 

 bones were well developed and freely movable, and by 

 the possession of a long lizard-like tail actually exceed- 



